


Vast Silver

by Papapaldi



Category: Doctor Who (2005), Horizon: Zero Dawn (Video Game)
Genre: Crossover, Gen, Post-Episode: Revolution of the Daleks, i can't believe i'm actually writing this
Language: English
Status: In-Progress
Published: 2021-01-27
Updated: 2021-01-27
Packaged: 2021-03-12 23:55:10
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 6,870
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29019321
Author URL: https://archiveofourown.org/users/Papapaldi/pseuds/Papapaldi
Summary: The Doctor and Yaz land in an abandoned corporate building approximately 975 years after the end of the world. Everything should be very, very dead. Instead, they find a world teeming with new life, and old enemies.
Relationships: Thirteenth Doctor & Yasmin Khan
Comments: 6
Kudos: 15





	Vast Silver

**Author's Note:**

> There was a prompt, it got away from me. Doctor Who and video games!!  
> So here comes a crossover I've wanted to do for a while, concerning two of my favourite sci-fi stories/characters of all time.  
> And then there's an AI called Vast Silver, and an AI called the Cyberium that is all silvery-y, so see!! it works!!  
> Mostly I just want Yaz to learn how to hunt machines, and explore the fact that Aloy and the Doctor are actually the same character??  
> Come on there's the mysterious origins, their sense of being the only ones left to save the world, and stand alone against all that threatens it :0 They're curious and logically-minded but deeply compassionated and curious and  
> ok I'll save it
> 
> Also, I’ve included an infodump via the Doctor’s never-ceasing explanations if you haven’t played the game.

Yaz shivers, hugging herself as she leans forward and pokes her head around the corner. As suspected, more cold corridors of frosted metal. The abandoned facility is dark, wet, and cold, just like the Sheffield winter she left behind. It’s far from the off-world tropical holiday she was secretly hoping for, but the Doctor seemed intent upon coming. Very intent, actually, in the telltale way her eyes narrowed, her lips thinned, and her brow wrinkled with cool concentration as she hunched over the TARDIS controls and punched in their current coordinates. Yaz asked her usual questions, and received her usual vague responses in return. 

Apparently something is here that’s not supposed to be, though where _here_ is, Yaz still isn’t clear on. 

At first, she thought it was a spaceship, on account of all the metal corridors and power cells and frozen computer components. Near the room where they landed, Yaz came upon laboratories, and offices debecked with cleared desks and fabric-coated chairs preserved in the permafrost. At this point, her spaceship theory was still fairly firm. Then, she found a window in one of the offices – one of the higher-ups, she suspected, from the floor-to-ceiling glass wall and all the legroom under the caved-in desk – and she saw that they were in a large skyscraper resting upon a frozen landscape. 

A blizzard raged tumultuous through the low cloud cover that mystified the ground below. From the clouds, the rusted frames of buildings reached up toward the window, and dark green vines clung to the side of the building for dear life. 

Yaz can still hear the Doctor’s Sonic buzzing away, echoing through the caverns. The stalactites above drip with metal rot and frozen mould. A splash of dark grey soaks her leather-clad shoulder. 

Judging by the furniture, the race that occupy this planet are bipedal and of human stature, but that doesn’t necessarily mean anything. Besides, there are plenty of human colonies out there amongst the stars. Except, Yaz thinks grudgingly, the sky was the right shade of greyish blue in the snow storm, and there were the right number of suns in the sky, and the general decor, despite its frozen, half-rusted state, looks like the sort you might find in a modern office building back home. Office core is basically universal, if their myriad trips are anything to go by. It’s probably nothing to worry about. 

Yaz follows the irritating whirr of the sonic out of the office of what was, a long time ago, no doubt a highly successful employee, and winds her way back through the chilly corridors. 

The building is coming apart, and it groans beneath her feet in pitchy whines and cracks of ice as frozen beams snap, and brittle slats shatter. Some areas of the building are completely inaccessible. Almost all of the doors are locked, sealed with a futuristic looking circular seal in their centres. 

It’s strange, generally when they step out of the TARDIS doors the Doctor has a speech prepared about where they are and why, whether they’re permitted to wander, or warned against danger. Now that it’s just Yaz along for the trip, maybe the Doctor assumes she can do without the warnings. Or perhaps she just knows Yaz won’t follow them anyway. 

When they landed, the Doctor went off into the dark, holding her spittling amber Sonic high with a murmur over her shoulder to stay put. Fat chance of that. 

“Doctor?” Yaz says, spying her darkened form at the end of the corridor. Yaz passes a room filled with models of dangerous-looking robots; spindle-limbed, many-toothed – half-tanks half-beasts, with scorpion’s tales and kraken’s jaws. She shivers as she wanders past, and only half from the cold. 

“Hmm?” The Doctor drops her arm to her side and turns to look back at Yaz, surprised. “I thought I told you to wait by the ship.”

“You weren’t very specific.”

“Yes, well,” she flashes Yaz a muted grin. “I think it was implied, don’t you?”

“I never assume anything,” Yaz says cheerfully, catching up with the Doctor. “Found something?”

“Nothing except complete and utter confusion.”

“Why?”

“Well we followed a signal here, like I said. Connection was a bit iffy, because it _really_ didn’t want us following, but we got here in a roundabout way. Only now it’s nowhere. Or possibly it’s everywhere.” The Doctor sniffs in the cold, and taps her screwdriver against her palm. It sputters out a protesting buzz. “And it’s cold.”

“Tell me about it.” Yaz wraps her arms more tightly around her body. She’s glad she brought the leather jacket with the fur collar, even if the fur is fake and scratchy and not particularly warm. 

“No, I mean it’s too cold. It’s a raging blizzard out there. Way too cold for the middle of –” the Doctor’s mouth hangs open in a guilty gape. 

It had to slip out at some point, even if Yaz has basically figured the truth out for herself already. She sighs. “Of what?” At the Doctor’s silence, Yaz mutters resignedly. “Just say it.” 

“Erm… well, sort of the middle south, actually –”

“Of where?”

The Doctor shifts from foot to foot, casting her eyes about. They skirt over the metal walls and engine-scented stalactites, and finally come to rest upon Yaz’s own. “Utah.” 

“Right,” Yaz sighs again, warm and white in the chill. It’s a wonder she can get enough air into her lungs for all the sighing she’s been doing lately. “Nuclear winter?” she asks hopefully. Maybe it’s only this region that’s a dilapidated, frozen ghost town. 

The Doctor shakes her head. “No radiation. Sorry, it’s err…”

“You’ve brought me to the end of the world, haven’t you? Again _._ ” Yaz breathes in the crisp, dead air. In through the nose, out through the mouth. Anger abated. 

“What year is it then?” she asks the Doctor. 

“Thirty forty-one.” She flashes Yaz a briefly-held sympathetic look, then takes up her Sonic once more and goes back to scanning. “Meant to say, thought we’d be out of here fairly quickly. I wouldn’t have brought you along at all, only it’s quite urgent.”

“Not really what I want to hear, but okay.” Yaz’s voice is quiet enough that the Doctor can comfortably pretend not to have heard her, though Yaz knows that she did. 

Yaz follows the Doctor through a few more locked doors that part obligingly with a whine of her Sonic. They make a satisfying whooshing noise when opened, as the biting air rushes across the divide. 

“So, how did the world end this time?” Yaz asks, in a conversational tone. It may as well be casual, seeing as different permutations of the apocalypse are becoming a regular occurrence for her. “Can’t see any spa resort, no Dregs. No Cybermen either.”

“Another potential apocalypse, currently favoured by the multiverse, or the time-soup, or the hand of fate – whatever you want to call it.” 

“I reckon I prefer the first one,” Yaz jokes. “So, what did it this time?”

“Well, from what I’ve gathered so far. Basically, giant killer robots.” Ryan would be having a field day. Well, no. The old Ryan would be having a field day. The new Ryan would be fed up with all the lying-by-omission and impending doom. 

“Like the models,” Yaz says, thinking back to the room she saw full of prototypes, or test models, or possibly marketing props. “I saw a room full of them back there somewhere.”

“This place used to be the richest corporation in the world, manufacturers of war machines. Faro Automated Solutions.” The Doctor taps a half-rusted sign beside one of the laboratory doors, brittle glassware preserved within. Half of the letters have been scratched away. 

“You see, in the future – well, in many potential futures encroaching on your early twenty-first century horizons – corporations grow, like creatures, or parasites, feeding off capital. More important than any government – in fact, their legions, when allied with the right bureaucrats and political mouthpieces, _are_ the government. They wage war with one another. They exchange territory in both business deals and on the battlefield. The shake of the hand, and the taking of lives.” They come upon a frozen stairwell, and begin a slippery descent. “It’s all automated,” the Doctor continues, calling up to Yaz whose trainers slide upon the ice to no end, “at least it was automated, by about twenty-sixty. So whoever has the most money gets the most expensive war robots, they win the battle, they take the spoils. The capital, the territory, the resources, the workers – they’re like turn-cloaks, except they turn in their letter of resignation and clock in with the competitors to churn out identical products on better benefits.”

“That’s ridiculous,” Yaz mutters. Her hand is stinging with cold from gripping the rusted bannister.

The Doctor shrugs. “So is the stock market. It’s all just belief. Faith changing hands. People live and die by the zig-zagging of little green and red lines, generations starve for the sake of probabilities. You’ve had the Great Depression, why not the Great War?”

Yaz hums thoughtfully, unsure of how to respond. She changes the subject from the arbitrary chaos of modern society to a far more pressing concern of hers. 

“So, let me guess, the war machines rebelled and killed everyone on the planet.”

“Well, sort of.” The Doctor stops for a moment, shutting her eyes. Yaz sidles past her upon the narrow landing and sees her eyelids twitching as her eyes move beneath them. Her lips form over half-pronounced words, mumbled inaudibly. 

“Are you okay?” 

“Mm? Oh yeah.” The Doctor opens her eyes, her lips stretching into a grim line. She strokes her fingertips over the metal wall and winces. 

“Chilly?”

“No, painful. Lots of guilt within these walls. Though I suppose you would be, if your company ended all life on Earth.”

“Sort of,” Yaz prompts the Doctor. “You said sort of. What really happened?”

The Doctor unlocks the door at the bottom of the stairwell, and awaiting them is a vast circular lobby, mezzanine floors ringing the walls in collapsed metal balconies above. In the centre, above an ice-coated reception desk, there is an enormous triangular logo emblazoned with the name _Faro_. 

“There was a glitch,” says the Doctor. “It severed the chain of command, and soon enough the top-of-the-line, Black Quartz encrypted killer robots answered to no one but themselves. No CEO, no company strategic division. Just the swarm.” The Doctor swallows thickly, and Yaz follows her into the lobby. “They replicated themselves at a precipitous rate, slaved any machines used against them to their secure network, and converted the biomass of the entire planet into fuel. They ate everything; the nutrients in the soil, the plants, the ungrown seeds, the animals,” she casts Yaz a furtive look, “the people. All within fifteen months. There was nothing to be done about it. Goodbye human race.” She sighs almost inaudibly, tired. Her arms droop by her sides. 

“There’s nothing but a wasteland out there now – not a single leaf, not a breath of air. And the monsters sleep, comatose, waiting for something alive to eat.” 

Yaz’s mouth is dry, despite the dank air. The Doctor is no longer walking or scanning, she simply stands before the monument to the company that engineered the end of days, looking up at the logo’s sleek angles that some long-dead graphic designer was likely once very proud of. 

“So it’s one of those poetic, engineers-of-our-own-demise type stories,” Yaz mutters. Her hands are stuffed into her pockets, and the tip of her nose feels raw. It’s colder here, on the ground floor, in the heart of the building, as if the systems that once kept the building pleasantly cool have leaked ice through the ducts and veins, and layered the marvel of minimalist architecture with a wintry sheen. 

“Poetic,” the Doctor turns to Yaz with a dark, inscrutable look in her eyes. “Yes, I suppose it is.”

“What a second,” Yaz says, thoughts slow to form, as if dragged through snow. “You said no air, no biomass.”

“That’s right – oh, yes, artificial oxygen shell. I extended it fairly far down from the TARDIS. We’re perfectly safe.” She takes a deep breath and jumps on the spot as if to prove this.

“Okay, but I saw vines growing on the side of the building,” Yaz says, remembering the dark leaves frozen to brittle spades in the wind. 

The Doctor’s face scrunches in confusion. “Are you sure?”

“Yes. Ivy or whatever, tangled all through the metal outside.”

“But that’s impossible – they weren’t plastic, were they?”

“Why would a swanky modern corporation stick plastic vines all over their headquarters?”

The Doctor shakes her head, shutting her eyes again. Yaz has seen her do this sort of thing before – on the stairwell, for instance, though it’s difficult to be sure. Sometimes she just stops for no reason at all. 

Right now, as she did earlier, the Doctor sifts through time, searching its lines, its permutations, pacing along strings of probability and picking out the logical sequence of events resulting from their simulation. Like the string of favourable moves in a chess game. She traces fault lines, and fate lines. Across a plateau or a palm.

Upon inquiry, the Doctor tends to brush the action off like it’s nothing, though the Doctor has explained it to them all on occasion, when they used to be an _all_ rather than a just-her. Yaz used to think it was modesty, though she knows better now. Some things are just too strange. Alien abilities lead to questions about said aliens, which leads, inevitably, to a home that the Doctor would rather forget. 

Yaz doesn’t know everything – only what Ryan relayed to her, and what little she has extracted from the Doctor since. Vague concepts, like hidden memories, a childhood that was not her own, or at least not her first, and a portal in the sky, an unknown planet. 

“Anything?” Yaz asks, as the Doctor’s silence begins to stretch. 

“No,” she shakes her head, more to clear her mind than to indicate a negative result. “Doesn’t matter anyway. Mystery filed away, see” – the Doctor puts her hand in her coat pocket, and her arm sinks in nearly up to her elbow. Something in the depths of her pocket clangs. “It’s on the back burner.”

Yaz chuckles. “You don’t have a back burner.”

“Sometimes I’ve got to, because we’re here for a reason, and impossible vines don’t matter.” Her furrowed brows tell Yaz that they matter very much indeed. “We’re here for what caused all this in the first place. Rocked up too late, but that’s not a new problem.” 

The Doctor smiles sheepishly at Yaz. No, definitely not a new thing. Seventy minutes late for a movie marathon with Yaz’s sister, and ten months late for a reunion with her grieving friends. Apparently, the TARDIS always takes the Doctor where she needs to go, which sounded to Yaz at the time a lot like what people always seem to say when tragedy strikes, that things always happen for a reason. 

“What are we here to do?” Yaz asks.

“Basically, we’re here to stop the end of the world.” 

“So we’re going back to the TARDIS, yeah? Can’t do much if the world has already ended.” 

“Right you are, Yaz.” The Doctor casts a longing look toward the entrance to the reception area, through which faint rays of white sunlight stream in jagged stripes across cannibalised metal and crumbling stone, migling in ruin. “But…”

“But?”

“But how could there be _vines_?” 

Yaz grins broadly, and the Doctor answers with a wicked, glinting smile of her own. She dashes off, skidding dangerously on the ice. Her arms pinwheel as she steadies herself and, in a flurry of pale blue, she clambers over the ruins and towards the beckoning sun. 

“Doctor, what about the air?”

“Well, if you’re certain they were vines – and I’m trusting you on this one Yaz – then there’s got to be air out there for them to grow in.” The Doctor’s voice has almost faded by the time Yaz, with a final glance up at the logo looming behind her, follows. 

With some precarious climbing, and difficult shifting of rubble involving the use of Sonic-generated telekinetic fields produced via connection to the computer components lodged in shrapnel shards amongst the stone, Yaz and the Doctor tunnel their way out of the ruins. 

They exit through a narrow fissure in a dark rock face, long fallen over the entrance in some cataclysmic impact with the surrounding mountains. From the ground, past the bitter torrents of snow, Yaz sees an overarching canopy of rusted metal entwined with hardy forest twine, dark and strikingly verdant in the pale sunlight. A ruined city sits, reclaimed by impossible vines, and there’s not a hungry war machine in sight. 

The Doctor pants up at the sky, wiping sweat from her reddened cheeks. “Look at that – air, vines – _life,_ finding its beautiful, impossible way. Time and time ag –”

In a splintered moment, an arrow whistles through the air and lands with a dull thunk against the rockface behind them, and onto the snow. Its crude metal tip sinks a few inches into the frost. Yaz and the Doctor look at each other in alarm. 

“No survivors?” Yaz whispers. “I’m pretty sure killer robots don’t shoot arrows.”

With a sharp breath, the Doctor faces forwards and puts her arms up. “Don’t shoot! My friend and I were just having a mosey around your lovely ruin here.” Yaz follows her example and puts up her hands as well. 

A figure comes into view, standing bulky and steadfast in the storm. It seems to come from nowhere, as if they were hidden in plain sight. 

A woman wrapped in colourful furs steps forwards, a brown bandana drawn up over her face. Her wild red hair dances behind her in streams of braids and beads and matted dreads. She holds a bow of wood and sharp metal, and an arrow knocked upon the string, with several more waiting in a quiver on her hip. Electronics pulse upon her furs, knitted together in a lattice upon leather. The metal discs glow, and extend a field of light in a faint blue, honeycombed pattern. Yaz knows a shield when she sees one. 

“Oh, hello,” the Doctor breathes. “Didn’t see you there. Look,” – she opens her jacket in a slow movement and shows the lack of weapons, and warmth, concealed within – “not armed, nothing on me. No need for weapons.” She nods pointedly at the arrow still pointed in her direction. 

The woman steps closer and lowers her weapon, sliding her arrow back into her quiver with a learned, fluid motion. She pulls the thick bandana from over her face, and Yaz almost gasps when she realises how young she is. She looks like a kid, wrapped up in all those furs – or she would if it weren’t for the battle hardened expression on her face. The sunspots and furrowed brows and sharp, focused eyes. 

“These ruins are dangerous,” the woman says. 

“More dangerous than being shot at with arrows?” Yaz replies in a scathing tone. 

“I was picking up… never mind.” She peers at Yaz with an expression of curiosity, tapping a small metal device fastened to her ear. “I’m sorry,” she says begrudgingly. “It was only a warning shot.” The woman’s eyes wander toward the Doctor, and wrinkle in confusion.

Next to Yaz, the Doctor’s eyes are wide, her mouth hanging open. “Elisabet!” she cries, surging forwards. “Elisabeth Sobeck!” at her approach, the woman shifts backwards, pulling a glowing, curve-bladed spear from her back in a swift motion, as if its bulk weighs nothing at all. The Doctor has the good sense to stop short. 

She peers at the woman quizzically, voice growing quiet. “No, that’s not right,” she mutters lowly, pacing to and fro. The woman stands defensively, but unmoving. Her grip quivers around the spear. “Oh, but it is, I remember.” The Doctor turns to Yaz and blathers an aside, “I was a professor at Stanford in 2037 – well, fake professor, technically my teaching license was twenty years too late and filed under a different face – but she, _you_ ,” she turns back to the woman with the spear. “You were the very best.” The Doctor stops pacing and claps her hands together, smiling exuberantly. “I’m a _really_ big fan.”

“Doctor,” Yaz says quietly, putting a hand on her shoulder and pulling her gently backwards. The Doctor shakes off Yaz’s grip. 

“But wait, getting ahead of myself,” she whispers. “I forgot the bit about this being impossible,” – she rounds on the woman that is quite possibly about to skewer them both. “This is impossible! How are you here?” the Doctor walks forwards, brushing past the spear unafraid. “How is anything here?” she looks up at the vine-crossed sky. “The world should have ended nearly a thousand years ago.” 

The expression on the woman’s face is almost pained. Pain, curiosity, confusion, elation, and something like fear as well. Her hand flicks toward a plastic globe fastened with twine around her neck. For a moment, she really does look like a child. 

Yaz catches her eye. “Are you alright?”

The woman glances at the Doctor, plastering on a brave face. Her hand moves back to her spear. “I am not Elisabet, though it’s an easy mistake to make.”

The Doctor looks over at her in wonder, eyebrows drawn in befuddlement. She fishes the Sonic out of her pocket, and points it at the woman. Again, she shrinks back, grip tightening. The Sonic blinks and spurts, and the Doctor brings the screen up to her face. “Yes,” she looks up at the woman from her hunched position. “You really are – but how _can_ you be?”

“My name is Aloy.” In a quick motion, Aloy buries the hilt of her spear in the snow and darts forwards, snatching the sonic from the Doctor’s hands before she can react. 

“Oi!” she complains, dashing after Aloy, but Aloy turns her back and holds the sonic reverentially in her fingerless-gloved hands. With one hand pressing the button on the Sonic, and the other suspended in the air beside the device on her ear, her fingers fiddling with thin air, her features twist in confusion. 

“This device…” she murmurs.

“Yep, great isn’t it. I’d quite like it back now.” The Doctor hovers nervously, a few paces away. 

“Doctor,” Yaz whispers, moving forward to stand beside her. The cold is beginning to become unbearable. “Not to be thick, but what’s happening?”

“Sonic reads her as Elisabet Sobeck, famous scientist of the late twenty-first century, definitely not a huntress from the thirty-first. She’ll probably be in your future, tends to crop up in a lot of potential timelines. Well, in all the good ones, anyway.”

“But what about the planet. How are there still people here if everything got eaten?” 

The Doctor’s mouth hangs open for a moment. Abruptly, she shuts it and glances at Yaz furtively. “Back burner, yeah? We’ve got a world to save. Right,” she addresses Aloy in a louder voice. “Sonic please.” 

“Sonic,” Aloy whispers, eyes still trained on the screwdriver. 

“Yup, made it out of spoons.”

Aloy takes one final, wistful look at the silver instrument, and hands it back to the Doctor, who can barely close her frigid fingers around it. Aloy continues to eye the Sonic with quiet hunger. 

“Right then Yaz, let’s get back to the ship.”

“Wait!” Aloy cries, wrenching her spear from the snow and stowing it upon her back. 

The Doctor presses her lips together, pale and bluish. Not exactly in impatience, Yaz observes, it’s more of a steeling grimace. Yaz can see how hard she is trying not to be drawn in by the enveloping mystery. Overhead, the vines seem to tease as they waver in the slowly calming winds. 

“What?” the Doctor asks brusquely, turning back to Aloy. 

“What tribe are you from?” There is a smirk to her lips that tells Yaz she knows that the question will trip them up.

“Freelancers,” the Doctor shrugs. 

“Yeah, that’s right,” Yaz nods along, her teeth chattering painfully. 

“I’ve never seen a device like that, not even my Focus,” – Aloy indicates the device on the side of her head in a tone that delineates a capital letter – “has ever seen anything like it. And your clothes… well for a start they aren’t nearly warm enough for you to have survived the trip, and I’ve only seen fabrics like that – neat stitching, vibrant patterns – in ancient holograms.” 

The Doctor’s jaw is tensed, caught between wanting to leave and wanting very badly to explain. 

“You know about Elisabet, and you talk like them too, the Old Ones. Freelancers, mosey, fan –” Aloy grins to herself. “You’re from some other settlement, aren’t you? Formed hundreds of years ago around another cradle facility.” Aloy begins to pace as she speaks, hands gesticulating stiltedly at her sides, half addressing herself, as if accustomed to often doing so.

“And Apollo, the record of human knowledge – there must have been a copy that survived the purge, that’s the only way. And a ship,” she wrinkles her brows, and glances up at the Doctor. “A ship, that’s what you said. I’ve only ever heard of… ships that flew.” She smiles brightly. “Planes, that’s it. But I – I’m not like the other people here. I know things they don’t. I understand what happened to the world, and what’s going to happen next, please.” Upon her panting chest, rising and falling beneath intricately stitched furs, the plastic trinket, the chipped-painted Earth, bobs up and down. “Please, I need your help. The terraforming system is starting to collapse – the core was blown apart, but it’s at Gaia Prime, it’s in,” – she searches for the right word with a grimace – “it’s in Colorado.” 

The Doctor is silent for a moment too long, and Aloy’s hopeful smile begins to fade.

“Yeah,” Yaz cuts in, stepping forwards. “Yeah you’re right, totally right. We’re here to help.” 

“Apollo was saved?” Aloy asks. 

“Sort of,” the Doctor pipes up, smiling grimly. “Shall we get back inside the ruin? Never thought I’d say it, but it’s warm in there.” 

With a nod, and a guarded expression that very poorly hides her excitement, Aloy follows Yaz and the Doctor back into fissure in the rock face. 

Aloy makes the journey look easy, slipping between narrows crevices and scrambling up precarious piles of rocks. Her numb fingers grip the ice slathered stone with ease. The Doctor and Yaz are far slower, and they emerge in the lobby panting and aching, while Aloy sits upon the reception desk flitting her fingers to and fro in mid air, a faint blue glow emanating from her Focus. 

“So, Aloy,” the Doctor calls, short of breath. Aloy grins in response, jumping down from the desk and shutting off her focus with a silent tap. “You said the terraforming system was collapsing.” The Doctor’s curiosity radiates palpably, and runs rampant through twitching fingers. 

“And it’s getting worse,” Aloy finishes. “The machines are deranged, the weather erratic, and I’ve heard rumours from the west. Red rot, and a storm, but I don’t think it’s natural. Of course the Carja –” The Doctor raises her eyebrows to indicate her confusion. Aloy continues obligingly. “– they’re the tribe occupying these lands – they say it’s normal, that the land to the west is cursed.”

“But you don’t believe in curses, is that right?” the Doctor smiles. She leads the way toward the door she and Yaz came through earlier. 

Aloy smiles in response. Yaz hangs back, watching the two of them. The Doctor’s eyes certainly do tend to wander, but Yaz can’t fault her for that. The world is full of incredible people, even at its very end. 

“They said I was a curse when I was born,” Aloy explains. “In Nora territory, not Carja, but they're just as superstitious. They lied, or invented, because they were scared. They made up a story.” 

“Right, because you must have been born in one of the…” the Doctor pauses under the pretence of unlocking a door with her Sonic. Aloy watches in awe, staring into the golden light as if looking at it hard enough might reveal its secrets. “Right,” the Doctor snaps her fingers, “cradle facilities, that’s it. Gestated from cloned DNA. Explains the uncanny resemblance to a long-dead scientist.” 

“Yes,” Aloy confirms. Apparently this is old news to her, and something that might have bothered Yaz a little more obviously, on an existential level. “Bu as far as the Matriarchs were concerned a motherless child had turned up on their metal altar.”

“And stories were spun, assumptions were made. Probably some prophecies too, am I right?”

Aloy smiles. “It’s almost like you know my life already.” 

“Nope, I’ve just dealt with plenty of tribal societies. Especially sisterhoods.” She makes a disgusted face, and presses on.

“So you haven’t heard anything about me?”

“No, totally fresh-faced. Never been in this neck of the… tundra.” The Doctor smiles, and Aloy seems somewhat appeased by the news. 

They come upon yet another locked door that, with a jolt, Yaz realises have all locked themselves after them. 

“Doctor?” Yaz asks, interrupting her and Aloy’s conversation. 

“Hmm?” the Doctor hums idly. 

“These doors, have they all locked themselves?”

“Ah,” she says, troubled. She taps the metal doorframe, and the walls respond with a resounding creak. “Must have.”

“No, they can’t have – you said you opened them already from the other side?” Aloy steps over the threshold and taps her Focus, reaching out to touch the broken circular pressure seal on the other side of the door. “This place suspended all operations centuries ago, the building has been dormant since before the Faro plague. I couldn’t even get through this way before. I had to do a lot more climbing.” 

“Ok, so,” Yaz says, following Aloy to the other side of the door. “So someone else is here.”

The Doctor bites her lip. “Someone else with a device powerful enough to awaken the door mechanisms of a millenia-dead automated office building. No, I don’t think so.”

“There was no one else on your ship?” Aloy inquires, glancing around at the hum of leaking pipes and groaning, rigid girders. 

“No one,” the Doctor concedes at a whisper, taking the lead. “Stay behind me.”

“Behind _you_?” Aloy asks scathingly. “You’re unarmed.”

The Doctor turns and winks. “Always.” Yaz resists the urge to roll her eyes, and settles upon a fond smile. 

They climb the many flights of slippery stairs back to the upper floors where the TARDIS waits, Aloy with far more grace than either of them, with her metal-plated snowshoes gripping the ice. 

Aloy explains that she came here tracing a strange signal during a five-day scouting trip west of an abandoned palace called Sunfall. She was searching for signs of new machines, dangerous beasts, she says, and Yaz and the Doctor pretend to know what she means. She calls it a hunter-killer. 

The Doctor, in her expert way, deflects nearly every one of Aloy’s prying questions. Aloy is sharp, though, and Yaz notices her shrewd expression deepening every time the Doctor manages to change the subject. Yaz eyes her quiver of arrows and sharpened spear worriedly. There are blood stains frozen upon the blade’s edge.

Eventually, they come upon the final locked door standing between them and the TARDIS. Yaz is unsure of what the Doctor will tell Aloy to get her out of the way while they make their escape, supposedly bound for some time in the past to stop this future from ever happening. Yaz isn’t sure how she feels about that plan – from what Aloy has said, there are many people living here. She mentioned refugees in the villages to the canyons to the south. She mentioned other tribes, unknown civilisations to the west – the human race, decimated, and somehow born again. She can tell that the Doctor is still desperately curious to find out how it happened. 

At her protest, Yaz can almost imagine what the Doctor would say. 

_We end lives all the time, stop potential futures in their tracks in every conceivable moment, every choice, and failure to choose. Do they weigh on your conscience?_

Yaz would, at that, likely keep her mouth shut, despite the fact that one could make the exact same argument against what the Doctor did by Lake Geneva in 1816, dooming the future to preserve a specific permutation of Yaz’s present. 

The Doctor unlocks the door, and the room beyond is empty. 

“Ah,” she says, glancing about worriedly. “Must be another floor up.” It’s definitely not. Despite the near-identical layout of every floor, Yaz recognises the office room with the tall window where vines still cling to the side of the skyscraper. 

“It isn’t,” Yaz says, stepping into the room. There’s even a square of indented frost upon the ground where the TARDIS used to be. 

“Your ship is gone?” Aloy asks. She has taken her spear from her holster and begins to pace around the outskirts of the room. She seems unable to keep still.

The Doctor dashes over to the square and points her Sonic at it. It buzzes feebly, then sparks in a flurry of white. “Ach!” the Doctor grimaces, shielding her face with one hand. “What’s the matter you?” She shakes the sonic frantically, as if it were a stubbornly silent maraca. 

“So, I’m guessing whoever locked all the doors also stole the ship, yeah?” 

“No,” the Doctor mutters, it’s impossible.”

“You said vines were impossible, and yet here we are.” Yaz goes to stand beside the Doctor, and the two of them peer dumbfoundedly at the patch of slightly darkened snow. 

“How could you fit a plane in here?” Aloy asks, from the other side of the room. “I thought we would be going to the roof. There’s nowhere to fly to.” 

Yaz widens her eyes at the Doctor and mouths; _‘what do we do?’_

Unhelpfully, the Doctor stares at the screen on the side of her sonic, her expression gradually descending the rungs of confusion, to shock, to horror. It stretches her face in a caricature of alarm. 

“Doctor?” Yaz asks uncertainly. 

“Remember when I said the signal we came looking for was sort of… everywhere.”

“Yes,” Yaz replies, closing her eyes and bracing for impact. 

“I’m starting to think that it might have been waiting for us, and as soon as we left, it snapped up the TARDIS in a very impossible surge of Artron energy.”

“Well it's not impossible, because it happened,” Yaz replies, growing frustrated. “Are you going to tell me what we’re following now?” It occurred to Yaz that, amongst all the excitement of vines and stories and human survivors, she had never asked. 

Aloy is eyeing them shrewdly, resting weight resting on her downturned spear. The Doctor glances conspicuously at her before turning back to Yaz. 

“This is a tribal society, the wealth of human knowledge was lost – nobody on this planet has the technology to abduct a TARDIS.”

“So it’s alien?”

“Aliens can’t do it either. No, only something from…” she sighs, staring at the sonic screen. “We were chasing a fragment of the Cyberium, Yaz, _and_ the Matrix, and, I suppose, quite probably the mangled consciousness of… well,” she smiles sadly, “malevolent evil. It was scattered across time and space in the Death Particle’s blast, flung from the pocket dimension housing Gallifrey into whatever eddied curls of space-time were unfortunate enough to be lurking amongst the potentialities on the other side.”

“So bits of the cyber AI got blown apart, and one of them landed on Earth.” 

The Doctor frowns thoughtfully. “In an extremely crude nutshell.”

“Right, so now it’s taken the TARDIS.” 

“No, but it’s broken, cut off from its source, totally powerless. It can’t have done this, not without _immense_ help.” She runs a weary hand over her face, straightening up. “Like I said, simple in and out, like crushing an ant, only far less cruel.” 

Despite their circumstances, Yaz smiles. “It’s never a simple in and out.” 

“No, I suppose you’re right.”

“Did you say…” Aloy’s voice sounds from close behind them. Evidently, neither of them heard her approach, despite her metal boot-soles. “Are you from another world, another... globe.” Absently, her fingers brush across the trinket around her neck. 

The Doctor rounds on her. “You don’t seem very surprised – maybe we’re mad.” 

“I know about spaceships,” Aloy says, her lips twisted in thought, and eyes wide with wonder. She hesitates, gripping her spear one-handed. It pulses dimly at her side, in time with the generators of the shield that flashes every few seconds, illuminating the still air around her. 

“I was raised to believe that a goddess created the world and that all the lands beyond her sight are cursed by metal demons. I’ve only recently come to terms with how very large this world is, and that it would take me a year without rest to walk its curved edge, and that most of it drowns in immense bodies of water.” Aloy smiles wryly to herself. “I saw the preserved image on my Focus of something called an Elephant – and I’ve never seen a creature so bizarre.” Beside her, Yaz feels the Doctor’s gait shift; downward to straight. Dejected to hopeful. 

Aloy continues with her chin held high. “There are wonders of the past that are lost to me forever and there is more to explore than I will ever be able to see. To me, it seems endless. Impossible. So,” she says, pivoting on the spot, addressing the floor, “It’s a logical extension that there are more worlds in the sky, beyond the stars. You can see them through the glass eyes they build in domes on the mountains in the Claim.” Aloy shuts her eyes, pushing out a slow breath. The Doctor is smiling. 

“I was raised in one valley, upon one mountain, in the sight of another, and was told that was it. That was all there was. But there is so much more out there.” Aloy opens her eyes again, her jaw tense and eyes blazing green. “I’ve met people who are mad, and they’re the wisest people I’ve ever known. So,” she adjusts her grip on her spear, and it gloves phosphorescent blue. “Let me know how I can help.” 

The Doctor turns to Yaz, smiling in bemusement. “That’s my Liz,” she whispers. 

“But you’re not from another settlement, are you?” Aloy asks. Her cheeks flush with embarrassment, mouth curling in thought. “You’re not here to help me rebuild Gaia?”

“I’m here to help,” the Doctor announces proudly, stepping forwards out of the square where the TARDIS used to be. “I’m going to do that however I can. Now,” she throws her Sonic in a spinning arc, catching it in a clean movement. “I’m getting a signal from the east. Pretty far east, actually. You mentioned hunter-killers, deranged machines, neighbouring tribes.”

“Yes,” Aloy nods. “The way is dangerous. Deadly, for most.”

“But not you, I’d wager. You look like you can handle yourself.” That she does. Now, sheltered from the storm and facing her head on, Yaz can see the scars that run across her face, one large white gash on her neck in particular, and the dark, calloused, knuckles that grip her spear. 

Aloy grins in a mockery of modesty. She tilts her head to one side. “Yeah, you could say that.”

“Aloy, you’ve seen my device, you’ve scanned it, seen how powerful it is. Trust me, I am _really_ good with machines. Building stuff, fixing stuff. I once took a radio apart and made a clockwork squirrel. It had voice-lines and –” Yaz nudges the Doctor, and she clears her throat. “Right, that doesn’t matter. If there’s a problem with your automated terraforming system, I’m your man.” The Doctor grins smugly. 

“But,” – she winces – “like I said, we’d probably be dead without an escort. So!” The Doctor claps, then holds out a hand for Aloy to shake. “Help us get back to our ship, and I’ll help rebuild your big old machine.” 

Aloy looks at the Doctor’s outstretched hand in confusion for a moment, but quickly grasps the essentials of what she’s expecting. She grips the Doctor’s hand gingerly. 

Yaz wonders if the Doctor is lying to Aloy, and if they will be leaving this barren future at the first chance they get, and promptly get to work stopping in from ever happening. She wonders if perhaps the Doctor will waste the effort of repairing their machine, to avoid a second apocalypse, only to erase any efforts she made in the first place. She would, if challenged, tell Yaz that kindness is never pointless, that time stretches on, no matter where and when they stick their oar in. Help is always worth giving. 

Looking at the Doctor’s smile as she shakes Aloy's hand with undue vigour, Yaz wonders if the trap is already closing, if the Doctor has once again found herself with an impossible call to make – to preserve the present, or save the future.

**Author's Note:**

> This chapter is just setup really. Next chapter we journey on toward Meridian!  
> Can't promise when, I keep starting new things dfjhgjdfkh  
> also, prepare for me to inject half-baked fan theories and speculation about HFW into this


End file.
